| Author |
Message |
    
Norm McIntosh
Visitor
| | Posted on Tuesday, July 24, 2007 - 08:06 pm: | 
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Hi: I have a problem with my dispro engine and I don't get it.
When the boat is NOT in the water, the engine starts great because it is not under any load from the water on the drive shaft and prop. When the boat is in the water it starts but runs very slowly and I can not get the rpms out of the engine. It wants to keep going but seems to have too much against it. I disconected the coupler from the crankshaft to the driveshaft and prop when the boat was in the water and the engine had lots of rpms. When I re-connected, the engine was very slow again and had a hard time to keep going. The driveshaft and prop are clear of any obstructions. Please help me if you can and thank-you very much.
Norm |
dave_myers
Member
Username: dave_myers
Post Number: 23
Registered: 11-2006
| | Posted on Tuesday, July 24, 2007 - 08:25 pm: |
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Hi Norm,
It appears that the Hull is moving when in the water as it is supported in a different manner than on the hard. I always do my shaft to motor alignment in the water. As you have mentioned, you disconnect the coupling and motor is free running. Bring the coupling up to the motor when in the water and see how far out of align it is and then shim the motor to suit. and your problems will be solved.
Cheers,
Dave |
john_archibald
Member
Username: john_archibald
Post Number: 15
Registered: 08-2006
| | Posted on Tuesday, July 24, 2007 - 08:42 pm: |
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I have never understood why people don't use the Oldham Coupling ( use the web to find info on the Oldham Coupling ) to connect the motor's shaft and the propeller shaft in boats. It has complete freedom for eccentric shafts and can even take a fair amount of angular misalignment.
I will be using a large one in my hull when I get her built.
Archibald |
jb_castagnos
Senior Member
Username: jb_castagnos
Post Number: 267
Registered: 07-2002
| | Posted on Tuesday, July 24, 2007 - 11:54 pm: |
|
If it is a misalignment the engine should be hard to turn and lose it's bounce, if it has a flanged coupling try turning it with the bolts tight and then loosen them and try turning it. If there's no noticeable difference I would suspect it's over propped of down on power. Has the boat been run with the prop that's on it? What's the pitch and diameter? |
miro
Senior Member
Username: miro
Post Number: 285
Registered: 11-2001
| | Posted on Sunday, July 29, 2007 - 09:29 pm: |
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Is the motor a copper jacket or a St Lawrence?
The copper jackets are designed to run at max 900 rpm with a 2 blade 9 in diameter prop.
A StLawrence will drive a 3 blade prop ( 9 in dia x 18 in pitch). A StLawrence going anything over 900 rpm will shake your DisPro apart in a season or two and you'll have a leaker of a boat.
The DisPro hull is meant for a modest engine and is not meant to go very fast.
In any case , alignment is quite important since there is not much power availabe and you've gotta get things right.
DisPros generally need almost everything to be right to work well - there is little or nno margin in any part of it.
What part of the coiuntry are you in? There is a DisPro Owners Association that is based in Toronto - also look at http://www.disappearingpropellerboat.com/
miro |
johnunderwood
Visitor
| | Posted on Thursday, September 27, 2007 - 05:17 pm: |
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I have just bought a 1925 Peterborough with a Dis Pro. I started once out of water with a hose hooked to intake and I feel engine is running in reverse rotation. I have not tried to run any more for fear of hurting engine. Is this possible. |
jb_castagnos
Senior Member
Username: jb_castagnos
Post Number: 291
Registered: 07-2002
| | Posted on Friday, September 28, 2007 - 05:19 am: |
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Two cycle engines will usually run in either direction, gear type water pumps won't cool in reverse. Some engines had the cylinders offset to reduce piston side load, but they will still run in either direction. It's common to run them both ways for forward and reverse if you don't have a reverse gear. If you put the timer towards you and pull it through compression it should start in the direction you're cranking. If you put the timer away from you and bounce against compression it will usually start in the other direction. If the motor has good compression and is tuned right starting on the bounce is easier than pulling through compression. |
junderwood
New member
Username: junderwood
Post Number: 1
Registered: 09-2007
| | Posted on Friday, September 28, 2007 - 07:16 am: |
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Thank you for the help and I am eager to try again. |
junderwood
New member
Username: junderwood
Post Number: 2
Registered: 09-2007
| | Posted on Wednesday, October 03, 2007 - 02:43 am: |
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Does anyone know where I can find a manuel for a Dis-Pro engine? |
ernie
Senior Member
Username: ernie
Post Number: 735
Registered: 01-2002
| | Posted on Wednesday, October 03, 2007 - 11:03 am: |
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There is a lot of info including how to run one in the book "The Greatest Little Motor Boat Afloat"
Google that and you will find plenty of them available.
Plus it's a really good book to read if you like old marine engines of any kind. |
jb_castagnos
Senior Member
Username: jb_castagnos
Post Number: 292
Registered: 07-2002
| | Posted on Wednesday, October 03, 2007 - 08:18 pm: |
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Dick Day's Palmer book has a lot of good 2 cycle info , it's available in the OME store. |
